A typical prior art head and disk system 10 is illustrated in FIG. 1. In operation the magnetic transducer 20 is supported by the suspension 13 as it flies above the disk 16. The magnetic transducer, usually called a “head” or “slider” is composed of elements that perform the task of writing magnetic transitions (the write head 23) and reading the magnetic transitions (the read head 12). The electrical signals to and from the read and write heads 12, 23 travel along conductive paths (leads) 14 which are attached to or embedded in the suspension 13. Typically there are two pairs of electrical contact pads (not shown); one pair each for the read and write heads 12, 23. Wires or leads 14 are connected to these pads and routed in the suspension 13 to the drive's control system (not shown). The disk 16 is attached to a spindle 18 that is driven by a spindle motor 24 to rotate the disk 16. The disk 16 comprises a substrate 26 on which a plurality of thin films 21 are deposited. The thin films 21 include ferromagnetic material which serves as the recording medium in which the write head 23 records the magnetic transitions in which information is encoded. The read head 12 reads magnetic transitions as the disk rotates under the air-bearing surface (ABS) of the magnetic transducer 20. Although use of air-bearings has dominated commercial disk drive, the use of hydrodynamic bearings is known. A hydrodynamic bearing exists when the magnetic transducer 20 skis on a liquid lubricant surface on the disk 16 as the disk rotates.
A thin layer of lubricant 25 is typically applied to disk 16 in drives using an air-bearing, as well as, those using a hydrodynamic bearing. A source of additional lubricant is needed during the life of the disk drive to replace lubricant which is lost through various mechanisms. Lubricant reservoir housing 34 contains lubricant packet 32 which forms vapor 35 which escape from the reservoir housing 34 into the internal environment of the drive and adsorbs on the disk 16. In some systems at least part of the lost lubricant is recaptured and returned to the reservoir for re-use. Typically, the geometry of the lubricant packet 32 is a thin rectangular structure that is comprised of synthetic and/or natural fibers or a suitable foam or sponge-like medium contained in a particle-free woven fabric covering or other particle-free medium. The lubricant packet 32 contains a specified quantity of volatile lubricant that is held inside the packet by capillary containment. The packet stores a specific volume of lubricant that is slowly transferred to the heads and disks to keep them constantly lubricated and bathed in a vapor of lubricant so as to prevent premature failure of the disk drive. However, in an active type of reservoir system, the lubricant packet is inserted into a device which will vary the amount of lubricant vapor based on sensor information.
A system for dynamically controlling the amount of lubricant being released from the reservoir has been described in U.S. Pat. No. 5,543,983 to Gregory, et al. The Gregory system is directed at a drive in which the head is supported above the disk by a hydrodynamic bearing. In this type of system the fly-height is directly affected by the thickness of the lubricant. The disclosed system obtains fly-height information from the drive's servo system to adjust the temperature of the lubricant in the reservoir to control the amount of lubricant vapor being emitted from the reservoir and therefore the thickness of the lubricant on the disk's surface.
What is needed is an improved system for controlling the amount of lubricant on the magnetic media.